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4 years ago

What does -9.8 m/s mean? And what does it mean if something has a negative velocity?

1 answer:

4 0

I can't guess what -9.8 m/s means until you tell me where it came from,
or what 'm/s' means.

If perhaps it has something to do with the acceleration of gravity on Earth,
then the correct figure is ' -9.8 m/s² '. That means that any object that
has no other force acting on it except gravity has its speed changing by
9.8 meters per second every second. Since it's gravity doing the job,
then the object's speed is either increasing down, or decreasing up.

If an object has negative velocity, then it's moving in the direction opposite
to the direction that you decided to call positive when you started doing the
problem.

For example, if you decide that up is positive and down is negative, and
then somebody drops a stone from the top of a tall building, then the
gravitational force on the stone is negative (pointing down), its velocity
is negative (it's falling towards down), and its acceleration is negative (its
speed towards down is getting faster and faster). Everything is negative,
only because you decided that up is positive and down is negative. It's
nothing to be worried about.

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Objects a and b each have a mass of 25 kilograms. object a has a velocity of 5.98 meters/second. object b is stationary. they un

mash [69]

The total kinetic energy of the system after collision is 223.5J

In elastic collision kinetic energy and momentum are conserved.

According to the question

mass of object a = 25kg

mass of object b = 25 kg

initial velocity of a u1 = 5.98 m/s

initial velocity of b u2 = 0

so from momentum conservation-

mau1 + mbu2 = (m1+m2)v

25kg × 5.98m/s + 25×0 = (25+25)v

v = 2.99 m/s

Now the total kinetic energy after the collision will be:

final kinetic energy = 1/2 (m1+m2) v²

= 1/2 (25+25)× (2.99)²

= 223.5 J

Thus, total kinetic energy of the system after collision is 223.5J

Learn more about elastic collision here:

brainly.com/question/1808045

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7 0

2 years ago

Ozone, O3 methane, CH4 oxygen gas, O2 Are classified as

erma4kov [3.2K]

I would think compounds.

5 0

3 years ago

Read 2 more answers

A 10 Kg dog is running with a speed of 5.0 m/s what is the minimum work required to stop the dog

ra1l [238]

Answer:

25J

Explanation:

Given parameters:

Mass of the dog = 10kg

Speed of the dog = 5m/s

Unknown:

The minimum energy required to stop the dog = ?

Solution:

The dog is moving with a kinetic energy and to stop the dog, an equal amount of kinetic energy generated must be applied to the dog.

To find the kinetic energy;

K.E = $\frac{1}{2}$ m v²

m is the mass

v is the velocity

Now insert the parameters and solve;

K.E = $\frac{1}{2}$ x 10 x 5 = 25J

8 0

3 years ago

A sound source A and a reflecting surface B move directly toward each other. Relative to the air, the speed of source A is 28.7

aleksandrvk [35]

(a) 1440.5 Hz

The general formula for the Doppler effect is

$f'=(\frac{v+v_r}{v+v_s})f$

where

f is the original frequency

f is the apparent frequency

$v$ is the velocity of the wave

$v_r$ is the velocity of the receiver (positive if the receiver is moving towards the source, negative otherwise)

$v_s$ is the velocity of the source (positive if the source is moving away from the receiver, negative otherwise)

Here we have

f = 1110 Hz

v = 334 m/s

In the reflector frame (= on surface B), we have also

$v_s = v_A = -28.7 m/s$ (surface A is the source, which is moving towards the receiver)

$v_r = +62.2 m/s$ (surface B is the receiver, which is moving towards the source)

So, the frequency observed in the reflector frame is

$f'=(\frac{334 m/s+62.2 m/s}{334 m/s-28.7 m/s})1110 Hz=1440.5 Hz$

(b) 0.232 m

The wavelength of a wave is given by

$\lambda=\frac{v}{f}$

where

v is the speed of the wave

f is the frequency

In the reflector frame,

f = 1440.5 Hz

So the wavelength is

$\lambda=\frac{334 m/s}{1440.5 Hz}=0.232 m$

(c) 1481.2 Hz

Again, we can use the same formula

$f'=(\frac{v+v_r}{v+v_s})f$

In the source frame (= on surface A), we have

$v_s = v_B = -62.2 m/s$ (surface B is now the source, since it reflects the wave, and it is moving towards the receiver)

$v_r = +28.7 m/s$ (surface A is now the receiver, which is moving towards the source)

So, the frequency observed in the source frame is

$f'=(\frac{334 m/s+28.7 m/s}{334 m/s-62.2 m/s})1110 Hz=1481.2 Hz$

(d) 0.225 m

The wavelength of the wave is given by

$\lambda=\frac{v}{f}$

where in this case we have

v = 334 m/s

f = 1481.2 Hz is the apparent in the source frame

So the wavelength is

$\lambda=\frac{334 m/s}{1481.2 Hz}=0.225 m$

8 0

3 years ago

A student holds an egg outside of an open window and let's go. The window is 40 meters above the ground and the egg is falling u

melisa1 [442]

The distance traveled by the egg after 2 seconds is 19.6 m.

The given parameters:

Height of the window, h = 40 m

The distance traveled by the egg after 2 seconds is calculated as follows;

$h = v_0_y t + \frac{1}{2} gt^2\\\\$

where;

$v_0_y$ is the initial vertical velocity of the egg = 0
g is acceleration due to gravity = 9.8 m/s²
t is the time of motion, = 2 s

$h = 0 \ + \ \frac{1}{2} \times 9.8 \times (2)^2\\\\h = 19.6 \ m$

Thus, the distance traveled by the egg after 2 seconds is 19.6 m.

Learn more about second equation of motion here: brainly.com/question/7977693

5 0

3 years ago